Frequency information rapid extraction for ranging applications

ABSTRACT

A frequency modulated continuous wave LiDAR system is disclosed that may be scalable and integrated in compact and demanding environments. The improved system of the present disclosure includes: an electro-optic modulator configured to modulate a laser generated by a laser source; a balanced photo detector configured to process an interference signal of a local copy of the laser coupled with a signal of the laser returned from a target and output a beatnote signal; a modulation source with two outputs, wherein the modulation source is configured to sweep in phase across a required bandwidth for the electro-optic modulator and the balanced photo detector; and a Frequency Information Rapid Extraction for Ranging Applications (“FIRE-RA”) system configured to: receive the interference signal from the balanced photo detector, process the interference signal with a signal from one of the two outputs of the modulation source for the balanced photo detector, and output distance and speed data for the target according to the processed interference signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is based on and claims priority to and benefit ofU.S. Provisional Patent Application No. 63/005,011, filed with theUnited States Patent and Trademark Office on Apr. 3, 2020. The entirecontent of the above-identified application is incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field ofLight Detection And Ranging (“LiDAR”), and more specifically toFrequency Modulated Continuous Wave (“FMCW”) LiDAR systems and methods.

BACKGROUND

LiDAR is a remote sensing method using laser light to measure distanceto an object. A flash or scanning LiDAR provides a three-dimensionalpoint cloud of the surroundings. Previous and current LiDAR navigationsystems (e.g., navigation systems on vehicles) relied on afirst-generation pulsed technology called Time-of-Flight (“ToF”) LiDAR.More recently, FMCW LiDAR provides an upgrade to the ToF vision systemand is advantageous due to the coherency in detecting the return signal.There is a demand to make the FMCW LiDAR system scalable and easilyintegrated in compact and demanding environments, such as an autonomousvehicle.

SUMMARY

Embodiments of the invention include a FMCW LiDAR system that may bescalable and easily integrated in compact and demanding environments,for example in autonomous vehicles. The improved FMCW LiDAR system ofthe present disclosure may include an electro-optic modulator configuredto modulate a laser generated by a laser source; a balanced photodetector configured to process an interference signal of a local copy ofthe laser coupled with a signal of the laser returned from a target andoutput a beatnote signal; a modulation source with two outputs, whereinthe modulation source is configured to sweep in phase across a requiredbandwidth for the electro-optic modulator and the balanced photodetector; and a Frequency Information Rapid Extraction for RangingApplications (“FIRE-RA”) system configured to: receive the interferencesignal from the balanced photo detector, process the interference signalwith a signal from one of the two outputs of the modulation source forthe balanced photo detector, and output distance and speed data for thetarget according to the processed interference signal.

The FIRE-RA system may provide simpler to develop and morecost-effective solution to the traditional frequency domain DSP systemsavailable on modern FMCW LiDAR products. It may pave the way to trulyscalable lower power vision solution that can still simultaneouslyextract radial velocity and distance information, without the overheadof common complex high-power FPGA chips.

These embodiments and others described herein are improvements in thefields of LiDAR and, in particular, in the area of FMCW LiDAR. Thevarious configurations of these devices are described by way of theembodiments which are only examples and are not intended to limit, butto provide further explanation of the invention as claimed. Othersystems, devices, methods, features and advantages of the subject matterdescribed herein will be apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, devices, methods, featuresand advantages be included within this description, be within the scopeof the subject matter described herein and be protected by theaccompanying claims. In no way should the features of the exampleembodiments be construed as limiting the appended claims, absent expressrecitation of those features in the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a schematic of an exemplary FMCW LiDAR system,according to some embodiments of the present disclosure.

FIG. 2 illustrates a schematic of an exemplary high-level schematic of aFMCW LiDAR system with a Frequency Information Rapid Extraction forRanging Applications, according to some embodiments of the presentdisclosure.

FIG. 3 illustrates a schematic of an exemplary FMCW LiDAR system with IQdemodulation configuration, according to some embodiments of the presentdisclosure.

FIG. 4 illustrates a schematic of an exemplary IQ demodulation opticalunit configuration, according to some embodiments of the presentdisclosure.

FIG. 5 illustrates a schematic of an exemplary high-level FIRE-RAbeatnote detection configuration, according to some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The following disclosure describes various embodiments of the presentinvention and method of use in at least one of its preferred, best modeembodiment, which is further defined in detail in the followingdescription. Those having ordinary skill in the art may be able to makealterations and modifications to what is described herein withoutdeparting from its spirit and scope. While this invention is susceptibleto different embodiments in different forms, there is shown in thedrawings and will herein be described in detail a preferred embodimentof the invention with the understanding that the present disclosure isto be considered as an exemplification of the principles of theinvention and is not intended to limit the broad aspect of the inventionto the embodiment illustrated. All features, elements, components,functions, and steps described with respect to any embodiment providedherein are intended to be freely combinable and substitutable with thosefrom any other embodiment unless otherwise stated. Therefore, it shouldbe understood that what is illustrated is set forth only for thepurposes of example and should not be taken as a limitation on the scopeof the present invention.

The ToF LiDAR had many disadvantages. For example, the received signalcan include noises due to daytime glare. There can be interferencesamong multiple systems in the same vicinity. The detection range can belimited. The FMCW LiDAR systems can provide an upgrade to the ToF visionsystem. The FMCW LiDAR systems can provide several advantages. Forexample, the FMCW LiDAR systems can provide coherent methods indetecting the return signal. In an FMCW LiDAR system, the return lightcan be interfered with a local copy of the initial signal making thedetection well shielded against outside noise that is not coherent withthe local copy.

The coherent interferometric nature of the FMCW LiDAR systems is thatthe dynamic range can be significantly larger due to the detected signalbeing proportional to the electromagnetic (“EM”) field itself, ratherthan the intensity (EM_(field) ²) of the sampling light. Additionally,the FMCW LiDAR systems may be able to observe the Doppler shiftinformation from a target, which can measure the speed/velocityinstantaneously versus a ToF systems that uses complex AI operations toestimate this during a sequence of frames. An exemplary FMCW LiDARsystem is described in PCT Patent Application No. PCT/US2018/059033,which is incorporated herein in its entirety.

FIG. 1 illustrates a schematic of an exemplary FMCW LiDAR system,according to some embodiments of the present disclosure. As shown inFIG. 1 , FMCW system 100 may include a narrow bandwidth laser source(e.g., diode) 110 that is modulated. Narrow bandwidth laser source 110can generate a laser 101, and a portion 130 of the laser is sent out toa target, while the rest is kept as a local copy and later interferedwith a return signal 140 from the target. In some embodiments, theportion 130 of the laser is split from splitter 112. In someembodiments, splitter 112 is a 75:25 splitter. In some embodiments, thelaser is further processed through an electro-optic modulator (“EOM”)111, an erbium-doped fiber amplifier (“EDFA”) 114, and an opticaltransceiver 115 as shown in FIG. 1 . In some embodiments, EOM 111 isconfigured to modulate laser 101 from narrow bandwidth laser source 110.

The resulting interference signal can be referred to as a beatnote (orsometimes as beat) 150 and can be recorded by a balanced photodetector(“BPD”) 116 in order to reject any common mode noise and further improvethe accuracy of the system. In some embodiments, BPD 116 can process aninterference signal of the local copy of the laser coupled with returnsignal 140.

In some embodiments, telecommunication grade components may be readilyavailable and suitable to use because of their high reliability andrelative availability. Moreover, telecommunication grade components aregenerally considered eye-safe, since their operation is usually limitedin the 1550 nm light spectrum. The light can be used as a carrierfrequency, on which a much lower modulation frequency can be inscribed.The modulation frequency is easier to sample than the hundreds ofterahertz (“THz”) frequency corresponding to the carrier at 1550 nmwavelength. A typical range of modulation frequency, to cover about2-200 meters of ranging distance, would have a bandwidth of 500-700 MHzat around 6 GHz of modulation frequency, with each modulation frequencycorresponding to a specific radial distance away from the LiDAR source.

However, one of the main struggles of an FMCW LiDAR system is the numberof points it can process, due to the entire spectrum of modulatedfrequencies needing to be sampled, sometimes at rates of 500 KHz ormore. For example, as shown in FIG. 1 , even though BPD 116 can samplethe modulation frequencies at once, the digital signal processing(“DSP”) system may not be trivial to make and usually involves at leastone high-speed (e.g., greater than 1 GHz) analog-to-digital converter(“ADC”) 181 and a field-programmable gate array (“FPGA”) 182 with morethan 2000 look-up tables (“LUTs”) in order to take a fast Fouriertransform (“FFT”) of the interfered signal and extract the necessaryinformation. For example, as shown in FIG. 1 , a specialized unit FFT184 can be implemented on FPGA 182 to take the FFT of the interferedsignal, after the signal has been processed by ADC 181. Moreover,scalability becomes an issue due to custom chip design being requiredevery time a parameter on the modulation frequency is changed, usuallyinvolving application-specific integrated circuit (“ASIC”) designs orother overkill solutions.

In addition, these complex FPGAs (e.g., FPGA 182 of FIG. 1 ) can havehigh thermal loads and consume power in the several tens to hundredWatts, which makes it impractical for integration in variousapplications (e.g., in autonomous vehicles).

There is a need for an FMCW signal processing system that is scalableand easily integrated in compact and demanding environments such asautonomous vehicles and provides other advantages as described herein.

Embodiments of the present disclosure provide methods and systems toresolve the issues described above. FIG. 2 illustrates a schematic of anexemplary high-level schematic of a FMCW LiDAR system with a FrequencyInformation Rapid Extraction for Ranging Applications, according to someembodiments of the present disclosure. As shown in FIG. 2 , FMCW LiDARsystem 200 may be scalable and easily integrated in compact anddemanding environments. It is appreciated that some components of FMCWLiDAR system 200 is similar to those described in FIG. 1 . For example,narrow bandwidth laser source 210, EOM 211, splitter 212, splitter 213,EDFA 214, and optical transceiver 215 can be similar to narrow bandwidthlaser source 110, EOM 111, splitter 112, splitter 113, EDFA 114, andoptical transceiver 115 shown in FIG. 1 , respectively.

FMCW LiDAR system 200 may include a Frequency Information RapidExtraction for Ranging Applications (“FIRE-RA”) 280 sampling andprocessing solution that may allow FMCW LiDAR system 200 to becomescalable and easily integrated in compact and demanding environments(e.g., autonomous vehicles). In some embodiments, exemplary benefits ofthis solution may include the following. First, scalar conversion fromfrequency to time domain can be achieved, and the need for FFTs can beavoided. Second, FMCW LiDAR system may allow using inexpensivecommercial off-the-shelf components (“COTS”). Third, 100 ps temporalresolution via a time-to-digital converter (“TDC”) which corresponds toabout 2 cm radial distance resolution can be allowed. Fourth, modulardesign can be used to reduce or eliminate the need for ASIC development(e.g., ASIC 183 or FPGA 182 shown in FIG. 1 ). Fifth, FMCW LiDAR system200 can use lower power consumption compared to a traditional FMCW DSPsystem. For example, FMCW LiDAR system 200 can use approximately 2 W inpower, which can be 7 times lower than a traditional FMCW DSP system.

In some embodiments, FMCW LiDAR system 200 can include a modulationsource 270 with two outputs. The outputs from modulation source 270 cansweep in phase across the required bandwidth for EOM 211 and the BPD 216shown in FIG. 2 . In some embodiments, this can be achieved with adirect digital synthesizer (“DDS”), or a splitter after a high power(e.g., 10 W RF) voltage-controlled oscillator (“VCO”), where thehigh-power channel drives the EOM and the splitter drives the samplingfor the BPD. In some embodiments, the DDS and the VCO can be a part ofmodulation source 270 shown in FIG. 2 . The advantage of the VCO setupis that off-the-shelf RF parts may be used and troubleshooting can bemade easy as the system may not require implementing a control of theoutput wave form such as when a DDS is used. For high-volumeimplementations, the DDS method may be preferred as it may provide majormanufacturing advantages.

In some embodiments, a FIRE-RA system may treat the output of a BPD as afixed RF frequency during the duration of one chirp cycle (e.g., 500 KHzrepetition rate), where modulation source 270 can ramp up the EOMmodulation from around 5.7 GHz to around 7.2 GHz. In some embodiments,modulation source 270 can be chosen for the optimal performance of theavailable COTS VCO. The BPD sampling channel can then be swept in syncwith the EOM and mixed in an radio frequency (“RF”) mixer in order toextract the frequency difference at which the BPD beatnote and the sweptlocal oscillator (“LO”) port on the mixer coincide. In some embodiments,the RF mixer can have a working range of approximately 0 to 1.5 GHz. Oneof the benefits over traditional high-speed ADC system is that thesampling occurs in an analog manner in the mixer rather than having tosample the entire output spectrum of the BPD with over >1 GS/sresolution. The FIRE-RA system's RF mixer simply detects when thebeatnote occurs and registers the waveform without having to keep trackof the information for the rest of the spectrum from the BPD. In someembodiments, if there are multiple frequencies on the BPD, multipledown-converted signals can be present at the output of the mixer. Thesecan be interpreted in later stages to extract radial Distance and Speedor velocity in case of the IQ Demodulation implementation of the FIRE-RAsystem.

In general, the FIRE-RA system can keep track of “when the beatnoteoccurs” and how many mixed frequencies between the modulation sourcebandwidth and the “fixed value” beatnote occurring. This can eliminatethe need of the use of FFTs, hence significantly reduces thecomputational power needed on the FPGA to calculate the radial Distanceand Speed values. In some embodiments, a FIRE-RA system may detect with5 cm total Distance accuracy or better over the range of 300 m away fromthe optical transceiver and extract at the same time the radial Speedwith a 0-156 mph range. This corresponds to two objects moving at 78 mphagainst each other, while keeping the thermal load under 2 W due to thelack of requirements on the FFTs and the high-speed ADC.

In some embodiments, in order to “locate” when the mixed frequencyoccurs in time, a band-pass filter (“BPF”) 281 can be applied at theoutput of the RF mixer in FIG. 2 . This can cut out a window around thefrequency of when the beatnote happens and allows for an envelopedetector 282 to register the occurrence. For example, each time theenvelope detector “sees” a modulation away from 0, it can track theoutline of the packet and outputs a pulse shape as a function of time.The advantage to such scheme is that there may not be a requirement knowthe actual shape of the beatnote, rather than tracking only “when itoccurs”. In some embodiments, through logic gates, the FIRE-RA systemcan extract a digital signal as a function of time that looks like asquare wave with a center at the peak of the beatnote occurrence time.In some embodiments, the information about the Doppler shift (or radialSpeed magnitude) can be preserved but the number of detected events andtheir location in time over the period of one chirp (e.g., 2 μs). Insome embodiments, band-pass filter 281 can be a band reject filter.

In some embodiments, a FIRE-RA system may include a TDC that candetermine the occurrence of the beatnote in time with an accuracy of 100ps, while the needed resolution in time to achieve 5 cm accuracy is 300ps. In this sense the FIRE-RA system has a significant margin to sparebefore it runs up against the limit of what the simple TDC can offer. Insome embodiments, the TDC uses an FPGA with a power of <1 W.

In some embodiments, a FIRE-RA system may output the TDC radial Distanceand Speed data coupled with an X and Y position information coming fromoptical transceiver 215 shown in FIG. 2 over an optimized SERDES cable(which saves space in control wires) and output it via an Ethernet cableusing a User Datagram Protocol (“UDP”) structure to a client such as avisualization system (“ROS”), an autonomous vehicle, or self-driving carAI unit. In some embodiments, the Distance and Speed data coupled withthe X and Y position information is measured from the target.

FIG. 3 illustrates a schematic of an exemplary FMCW LiDAR system with IQdemodulation configuration, according to some embodiments of the presentdisclosure. It is appreciated that some components of FMCW LiDAR system300 shown in FIG. 3 is similar to those described in FIG. 2 . Forexample, narrow bandwidth laser source 310, EOM 311, splitter 312, EDFA314, and optical transceiver 315 can be similar to narrow bandwidthlaser source 210, EOM 211, splitter 212, EDFA 214, and opticaltransceiver 215 shown in FIG. 2 , respectively.

As shown in FIG. 3 , FMCW LiDAR system 300 may use an IQ demodulationoptical unit 360 to keep a relative phase difference between twoseparate copies (e.g., with 45 degree phase difference, circularpolarization) of the optical LO in the system and interfere themseparately with the Rx beam to achieve a separation between so called Iand Q channels. In some embodiments, the two copies are interferedseparately with 50% of the Rx beam. In some embodiments, the directionof the Doppler shift may then be extracted based on the phase shiftbetween the beatnotes in both channels terminated by a BPD each. In someembodiments, the I channel implores a standard FIRE-RA detection scheme,while a copy of it is mixed against the Q channel to extract the phasedifference between the two, which ultimately yields to the direction ofthe Velocity vector. One of the benefits of using the mixer between thetwo channels is that a slow ADC 388 can then extract the phasedifference, optimizing cost and thermal load of the system. The“positive” or “negative” value is then assigned to the UDP packet above.

FIG. 4 illustrates a schematic of an exemplary IQ demodulation opticalunit configuration, according to some embodiments of the presentdisclosure. It is appreciated that the IQ demodulation optical unitconfiguration shown in FIG. 4 can be incorporated into FMCW LiDAR system300 shown in FIG. 3 (e.g., as IQ demodulation optical unit 360). Asshown in FIG. 4 , the IQ demodulation optical unit configuration mayallow for distinguishing the sign of the radial velocity vector. Forexample, the sign of the radial velocity factor can be distinguished bytracking the phase difference of the I and Q channels. The unit'spurpose is to physically generate the beatnote between the LO and thereceived Rx beam and separate the output as projections on twoorthogonal polarization axes.

In some embodiments, similar to FIG. 2 , the LO oscillator in FIG. 4 maybe mixed with the Rx beam. However, the LO may be converted to acircular polarization in free space (e.g., via means of a quarter-waveplate). This may establish a reference for the system. In someembodiments, the Rx beam may also be separated into equal projectionsover the orthogonal polarization axes, but rather than having a delaybetween them, it may simply be rotated by means of a half-wave plate.The circular LO and the linear but rotated in polarization Rx beam mayinterfere at a non-polarizing beam splitter and may then be split intothe separate components via polarizing beam splitter. In someembodiments, there may be a 50% loss in signal, which can be furtherimproved via adding another set of polarization splitting channel. Insome embodiments, the 50% loss may be acceptable for generating areliable beatnote signal.

In some embodiments, the generated beatnote may then be constantlyrotating one direction or another depending on the sign of the Dopplershift on the Rx beam. The two channels, I and Q, can be electronicallytracked. For example, the two channels can be tracked via a simple mixerthat takes a copy of the output of the two PBDs and extracts the phaserelationship sign. In some embodiments, the phase relationship sign maythen be fed into an ADC, as shown in FIG. 3 .

FIG. 5 illustrates a schematic of an exemplary high-level FIRE-RAbeatnote detection configuration, according to some embodiments of thepresent disclosure. It is appreciated that the beatnote detectionconfiguration shown in FIG. 5 can be incorporated into FMCW LiDAR system300 shown in FIG. 3 . As shown in FIG. 5 , the FIRE-RA beatnotedetection configuration may allow for real-time, non-FFT FMCW LiDARsignal processing. It is appreciated that some elements in FIG. 5 aresimplified, and more detailed steps may be presented in FIG. 2 , FIG. 3, or FIG. 4 . As shown in FIG. 5 , the optical beatnote frequency may betreated as fixed after the moment of occurrence, while a modulationsweeping source may be constantly sweeping across the bandwidth of theBPD. The mixer may downconvert the beatnote and a bandpass filter mayisolate a portion of the oscillations that is within the range ofinterest for the envelope detector. The envelope may then be binned andsampled (e.g., via means of a TDC), converted from time to distance andvelocity information (e.g., based on the number of peaks detected in onechirp ramp) and may be coupled with X and Y position information thatresults in a point cloud. The point cloud may be sent over UDP to avisualization device such as laptop but could be directly fed into an AI(e.g., AI in an autonomous vehicle) for further analysis.

Each of the processes, methods, and algorithms described in thepreceding sections may be embodied in, and fully or partially automatedby, code modules executed by one or more computer systems or computerprocessors comprising computer hardware. The processes and algorithmsmay be implemented partially or wholly in application-specificcircuitry.

The various features and processes described above may be usedindependently of one another or may be combined in various ways. Allpossible combinations and sub-combinations are intended to fall withinthe scope of this specification. In addition, certain method or processblocks may be omitted in some implementations. The methods and processesdescribed herein are also not limited to any particular sequence, andthe blocks or states relating thereto can be performed in othersequences that are appropriate. For example, described blocks or statesmay be performed in an order other than that specifically disclosed, ormultiple blocks or states may be combined in a single block or state.The examples of blocks or states may be performed in serial, inparallel, or in some other manner. Blocks or states may be added to orremoved from the disclosed embodiments. The examples of systems andcomponents described herein may be configured differently thandescribed. For example, elements may be added to, removed from, orrearranged compared to the disclosed embodiments.

The various operations of methods described herein may be performed, atleast partially, by one or more processors that are temporarilyconfigured (e.g., by software) or permanently configured to perform therelevant operations. Whether temporarily or permanently configured, suchprocessors may constitute processor-implemented engines that operate toperform one or more operations or functions described herein.

Similarly, the methods described herein may be at least partiallyprocessor-implemented, with a particular processor or processors beingan example of hardware. For example, at least some of the operations ofa method may be performed by one or more processors orprocessor-implemented engines. Moreover, the one or more processors mayalso operate to support performance of the relevant operations in a“cloud computing” environment or as a “software as a service” (SaaS).For example, at least some of the operations may be performed by a groupof computers (as examples of machines including processors), with theseoperations being accessible via a network (e.g., the Internet) and viaone or more appropriate interfaces (e.g., an Application ProgramInterface (API)).

The performance of certain of the operations may be distributed amongthe processors, not only residing within a single machine, but deployedacross a number of machines. In some embodiments, the processors orprocessor-implemented engines may be located in a single geographiclocation (e.g., within a home environment, an office environment, or aserver farm). In other embodiments, the processors orprocessor-implemented engines may be distributed across a number ofgeographic locations.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in configurations may beimplemented as a combined structure or component. Similarly, structuresand functionality presented as a single component may be implemented asseparate components. These and other variations, modifications,additions, and improvements fall within the scope of the subject matterherein.

As used herein, like elements are identified with like referencenumerals. The use of “e.g.,” “etc.,” and “or” indicates non-exclusivealternatives without limitation, unless otherwise noted. The use of“including” or “includes” means “including, but not limited to,” or“includes, but not limited to,” unless otherwise noted.

As used herein, the term “and/or” placed between a first entity and asecond entity means one of (1) the first entity, (2) the second entity,and (3) the first entity and the second entity. Multiple entities listedwith “and/or” should be construed in the same manner, i.e., “one ormore” of the entities so conjoined. Other entities may optionally bepresent other than the entities specifically identified by the “and/or”clause, whether related or unrelated to those entities specificallyidentified. Thus, as a non-limiting example, a reference to “A and/orB,” when used in conjunction with open-ended language such as“comprising” can refer, in one embodiment, to A only (optionallyincluding entities other than B); in another embodiment, to B only(optionally including entities other than A); in yet another embodiment,to both A and B (optionally including other entities). These entitiesmay refer to elements, actions, structures, steps, operations, values,and the like.

Although an overview of the subject matter has been described withreference to specific embodiments, various modifications and changes maybe made to these embodiments without departing from the broader scope ofembodiments of the specification. The Detailed Description should not tobe taken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims, along with the full range ofequivalents to which such claims are entitled. Furthermore, relatedterms (such as “first,” “second,” “third,” etc.) used herein do notdenote any order, height, or importance, but rather are used todistinguish one element from another element. Furthermore, the terms“a,” “an,” and “plurality” do not denote a limitation of quantityherein, but rather denote the presence of at least one of the articlesmentioned.

What is claimed is:
 1. A frequency modulated continuous wave (“FMCW”)LiDAR system, comprising: an electro-optic modulator configured tomodulate a laser; a balanced photo detector configured to process aninterference signal of a copy of the laser coupled with a signal of thelaser returned from a target and output a beatnote signal according tothe interference signal; a modulation source comprising two outputs,wherein the modulation source is configured to sweep in phase for theelectro-optic modulator; a Frequency Information Rapid Extraction forRanging Applications (“FIRE-RA”) system configured to: receive thebeatnote signal from the balanced photo detector, process the beatnotesignal with a signal from one of the two outputs of the modulationsource for the balanced photo detector, and output distance and speeddata for the target according to the processed beatnote signal; and anIQ demodulation optical unit communicatively coupled to the balancedphoto detector, wherein the IQ demodulation optical unit is configuredto keep a relative phase difference between two local copies of thelaser and interfere any of the two local copies of the laser with asignal of the laser returned from the target.
 2. The FMCW LiDAR systemof claim 1, wherein the modulation source comprises a high powervoltage-controlled oscillator and a splitter, the high-powervoltage-controlled oscillator is configured to drive the electro-opticmodulator, and the splitter is configured to drive the balanced photodetector.
 3. The FMCW LiDAR system of claim 1, wherein the FIRE-RAsystem is further configured to: process the beatnote signal byextracting a frequency difference at which the beatnote signal and thesignal from one of the two outputs of the modulation source for thebalanced photo detector coincide.
 4. The FMCW LiDAR system of claim 3,wherein the FIRE-RA system comprises: a radio frequency mixer configuredto extract the frequency difference.
 5. The FMCW LiDAR system of claim4, wherein the FIRE-RA system further comprises: a band-pass filter or aband reject filter communicatively coupled with the radio frequencymixer, wherein the band-pass filter or the band reject filter isconfigured to cut out a window around the frequency of when a beatnoteoccurs on the beatnote signal, and an envelope detector communicativelycoupled with the band-pass filter or the band reject filter, wherein theenvelope detector is configured to register an occurrence of when abeatnote occurs on the beatnote signal.
 6. The FMCW LiDAR system ofclaim 5, wherein the FIRE-RA system further comprises: a time-to-digitalconverter communicatively coupled with the envelope detector, whereinthe time-to-digital converter is configured to determine the occurrenceof the beatnote in time.
 7. The FMCW LiDAR system of claim 1, whereinthe FIRE-RA system is further configured to detect with a 5 cm or betterdistance accuracy over a range of 300 meters away while keeping athermal load of 2 watts or lower.
 8. The FMCW LiDAR system of claim 1,further comprising: a client configured to receive the distance andspeed data from the FIRE-RA system.
 9. The FMCW LiDAR system of claim 8,wherein the client is an autonomous vehicle.
 10. The FMCW LiDAR systemof claim 1, wherein the distance and speed data for the target furthercomprises X and Y position information for the target.
 11. The FMCWLiDAR system of claim 1, wherein the IQ demodulation optical unit isfurther configured to interfere each of the two local copies of thelaser separately with 50% of the signal of the laser returned from thetarget.
 12. The FMCW LiDAR system of claim 1, wherein an output of thebalanced photo detector is treated as a fixed RF frequency during aduration of one chirp cycle.
 13. A frequency modulated continuous wave(“FMCW”) LiDAR system, comprising: an electro-optic modulator configuredto modulate a laser; a balanced photo detector configured to process aninterference signal of a copy of the laser coupled with a signal of thelaser returned from a target and output a beatnote signal according tothe interference signal; a modulation source comprising two outputs,wherein the modulation source is configured to sweep in phase for theelectro-optic modulator; a Frequency Information Rapid Extraction forRanging Applications (“FIRE-RA”) system configured to: receive thebeatnote signal from the balanced photo detector; process the beatnotesignal with a signal from one of the two outputs of the modulationsource for the balanced photo detector; using a radio frequency mixer,process the beatnote signal by extracting a frequency difference atwhich the beatnote signal and the signal from one of the two outputs ofthe modulation source for the balanced photo detector coincide; using aband-pass filter or a band reject filter communicatively coupled withthe radio frequency mixer, cut out a window around the frequency of whena beatnote occurs on the beatnote signal; using an envelope detectorcommunicatively coupled with the band-pass filter or the band rejectfilter, register an occurrence of when a beatnote occurs on the beatnotesignal; and output distance and speed data for the target according tothe processed beatnote signal.
 14. A method comprising: modulating,using an electro-optic modulator, a laser; processing, using a balancedphoto detector, an interference signal of a copy of the laser coupledwith a signal of the laser returned from a target; outputting a beatnotesignal according to the interference signal; sweeping, by a modulationsource comprising two outputs, in phase across a bandwidth for theelectro-optic modulator; receiving, using a Frequency Information RapidExtraction for Ranging Applications (FIRE-RA) system, the beatnotesignal from the balanced photo detector; processing, using the FIRE-RAsystem, the beatnote signal with a signal from one of the two outputs ofthe modulation source for the balanced photo detector; outputting, usingthe FIRE-RA system, distance and speed data for the target according tothe processed beatnote signal; and using an IQ demodulation optical unitcommunicatively coupled to the balanced photo detector, maintaining arelative phase difference between two local copies of the laser andinterfering any of the two local copies of the laser with a signal ofthe laser returned from the target.